Arrowhead (Sagittaria latifolia), also known as duck potato, is a perennial aquatic plant that is native in most of North America. The large, arrow-shaped leaves grow up to three feet tall, and the plants produce small edible tubers, which are white or purple. They have a nutty flavour which is sometimes compared to chestnuts, and they are often prepared like potatoes, although they are also eaten raw.

Arrowhead tubers are sometimes collected from the wild, but they can more easily be cultivated in either wet soil or a water garden. However, since the tubers often grow a long way from the parent plant, growing arrowhead in a pot makes harvesting much easier. A wide, shallow pot, with gravel covering the soil, can be placed up to two feet deep in a water garden, or a large pot containing the plant can simply be placed in a slightly larger pot containing water to keep the soil consistently wet.

Arrowhead can be grown from seed, but it is more easily grown from tubers. Plants should be spaced about four feet apart in ponds, or one to three plants can be grown in a large pot in full sun. The tubers can be harvested when the plants begin to die back at the end of the season. Leaving several tubers behind will ensure a good harvest for next year.

Sagittaria graminea, Chinese arrowhead, can also be grown. These tubers can be harvested anytime during the year, but they must be protected from freezing. If you wish to grow arrowhead which is generally considered hardy through Zone 3, check the Latin name, and grow Sagittaria latifolia. If you are unable to find plants locally, they are available from Moore Water Gardens, which is also a good source of information about water gardening.

Sorry Middle Earth, I don't have a water garden, so no personal experience with these plants. Since they grow wild over such a large range, however, I wouldn't expect them to be difficult. A kiddie pool would make a low-commitment water garden that you could try them in. Good luck if you do!